<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style>
ul,li{
padding: 0;
margin: 0;
}
li{
padding: 10px;
margin: 10px;
border: 1px solid;
list-style: none;
}
.back{
position: fixed;
padding: 10px;
right: 20px;
bottom: 20px ;
cursor: pointer;
background: black;
color: white;
display: none;
}
</style>
</head>
<body>
<ul class="ct">
<li>111</li>
</ul>
<button class="btn">添加列表</button>
<div class="back">回到顶部</div>
<script type="text/javascript" src="js/jquery-3.2.0.min.js" ></script>
<script>
$(".btn").on("click",function(){
var str="<li>添加的列表</li>"
$(".ct").append(str);
})
//回到顶部函数
var $back=$(".back")
$(window).scroll(function(){
var top=$(window).scrollTop()
if(top>100){
$back.css("display","block")
}
})
$back.on("click",function(){
$(window).scrollTop(0)
})
</script>
</body>
</html>
图片.png
